The present invention relates to a recording apparatus for selectively recording images in black and colors other than black. More particularly, the present invention relates to, but not limited to, an electrophotographic recording apparatus of the type having a photoconductive element, means for providing an electrostatic latent image corresponding to image light on the photoconductive element, a device for developing the latent image to produce a visible image, means for transferring the visible image onto a paper, and means for cleaning the photoconductive element after the image transfer, whereby images are selectively recorded in a plurality of different colors.
Prior art color copiers which belong to a family of recording apparatuses include a one in which liquid developers of different colors are supplied to a single developing unit, as disclosed in Japanese Patent Publication No. 54-43898 by way of example. Another type of prior art color copier, i.e., monocolor type color copier is furnished with the same number of powder type developing units which may be selectively mounted in a body of the copier.
A problem with the single developing unit type scheme is that because liquid developers of different colors are fed to the single developing unit, colors used one after another for recording are mixed together resulting in an impure recording. Another problem is that several copies have to be wasted before a desired pure color is obtained. Further, any developer collected from the developing unit into a developer vessel is tainted by a color previously used, contaminating the whole developer stored in the vessel. This make it necessary for the developing unit to be cleaned every time the recording color is changed. On the other hand, the multiple developing unit type scheme suffers from a drawback that replacing the developing unit mounted in a copier body is troublesome and, in addition, the substantial number of mechanical elements, particularly those which are independent of a copier body, are awkward to handle.
In the light of the above, a handy color recording apparatus of the first-mentioned type is constructed such that in the event of a change of color the developing unit is cleaned and, then, supplied with a developer of another color.
To clean the developing unit, a vessel which stores a cleaning agent is provided so that the cleaning agent may be circulated to serve the cleaning function. In operation, it is not usual that the recording color is changed frequently and, rather, it often occurs that only a color change command is entered on an operating board. Generally, therefore, it is only after a change of recording color has been commanded and, then, a recording operation in the desired color has been commanded that an actual color changing process and the subsequent recording process are performed. Specifically, so long as the operation does not proceed farther than the entry of a color change command, the recording apparatus is held in a standby mode with one of its developer supply systems associated with the previous color selected. That is, in such a recording apparatus, after a particular recording color has been entered and data has been recorded in that color, the developer supply system adapted for the developer of the color used is maintained in an operable state. Such stems from the fact that the probability for data to be recorded consecutively in the same color is great, and the fact that the recording color is not changed frequently, i.e., the operation often does not go beyond the entry of a color change command.
As stated above, the recording apparatus is held inoperative with its developer supply system and developer collection system changed over to those which are associated with a color used immediately before. Hence, before starting a recording operation with a developer of new color, the developing unit is cleaned by replacing the developer supply and collection systems with, respectively, a cleaning agent supply and a collection system and, the, replacing the latter with a developer supply and a collection system adapted for the new color. This is followed by an actual recording process. Such a procedure results in a disproportionately long color changeover time.
Further, should the developer supply and collections systems associated with a color used immediately before be continuously held ready for operation, a long time of suspension of operation of the recording apparatus would cause a trouble to occur in the mechanism of a part of the developer supply and collection systems. If the change of color is incomplete due to such a trouble, the previous color is apt to be mixed with a new color. It is therefore preferable that when a long time of suspension of operation is presupposed. the developer supply and collection systems be replaced with the cleaning agent supply and collection systems.